1. Field of the Invention
This invention relates to an opening/closing mechanism for use in a double-sliding door having a circular-arc sectional shape in a horizontal plane and arranged to be closed at a central abutting position (which is referred to hereinbelow simply as "circular-arc shaped sliding door"), and more particularly to an opening/closing mechanism for use in a circular-arc shaped sliding door including a transverse frame having a circular-arc horizontal sectional shape and mounted on the upper parts of a pair of left and right door bodies; a drive pulley and a driven pulley mounted on the one circumferential end of the transverse frame and on the other end thereof, respectively; and an endless belt wound between and around the drive pulley and a driven pulley, the pair of door bodies being connected in place to the endless belt so that they may be slidably moved in opposite direction with each other.
2. Disclosure of Prior Art
A prior art opening/closing mechanism for use in a circular-arc shaped sliding door is known, for example, from Japanese Utility Model Application Laid-Open Specification No. SHO-62-187078.
Stating in brief, this opening/closing mechanism for use in a circular-arc shaped sliding door is arranged such that, as shown in FIG. 1, each of a pair of door bodies 1, 1 having a circular-arc horizontal sectional shape can be moved along each of guide rails (not shown) each having a circular-arc horizontal sectional shape; a pair of endless belts 2, 2 are arranged in respective loops in their respective horizontal planes along their respective guide rails; each of the endless belts 2 is connected to each of the door bodies 1; a drive pulley 3 for one of the endless belts 2 is connected to a motor 4, and driven pulleys 5 and 6 are mounted adjacent to each other so that a gear 7 coupled concentrically with the driven pulley 5 can mesh with a gear 8 coupled concentrically with the driven pulley 6, the arrangement being made such that when the motor is driven the pair of endless belts 2, 2 are turned in opposite directions relative to each other so that the pair of door bodies 1, 1 may be moved either in the opening direction or in the closing direction to thereby open or close the door.
In such an opening/closing mechanism, the pair of door bodies 1, 1 can be moved by means of one set of motors 4, however, provision of a pair of endless belts 2, 2 is required to move the pair of door bodies 1, 1, respectively, and also interlocking of the gears 7, 8 is required to enable the pair of endless belts 2, 2 to be turned synchronously at the same speed. If changes in backlash between the gears 7 and 8 or changes in the lengths of the pair of endless belts 2, 2 occur, then it becomes sometimes impossible to move the pair of door bodies 1, 1 synchronously at the same speed, thereby making it impossible to ensure that the circular-arc shaped sliding door can be opened and closed satisfactorily.
Further, in the above-mentioned prior art opening/ closing mechanism, since each of the endless belts 2, 2 is wound between and around the pulleys located at both ends and bent in a circular-arc shape in a horizontal plane along the moving locus defined by the door body 1, it is necessary to arrange the mechanism such that inner guide rollers 9a are kept in contact with the outer surface 2a of the endless belt 2 and outer guide rollers 9b are kept in contact with the inner surface 2b thereof.
To cope with this, if a toothed belt is used as the endless belt 2 to prevent the belt from slipping relative to the pulley, then, because the outer guide rollers 9b are kept in contact with the teeth formed on the endless belt 2, it is necessary to use toothed rollers as the outer guide rollers 9b to enable the endless belt 2 to be guided smoothly. However, the use of toothed rollers as the outer guide rollers 9b entails a disadvantage in that noise is generated when the toothed rollers are engaged with and disengaged from the tooth on the endless belt, and because of provision of a plurality of outer guide rollers 9b, the level of the noise which occurs when the circular arc shaped door is opened or closed becomes high.